This particular way of cooking fish is well known especially in West Java, Indonesia. Basically, it is a dish of fish spiced up with certain exotics ingredients, wrapped in fresh banana leaves. Banana leaves are essential as some believe it will make the smell and the taste of the fish better.
I even learned from my sister in law who came originally from Sukabumi (located in the very heart of West Java area), she suggested to shortly preheat the fresh banana leaves on a small (stove) fire, until the leaves a little brownish and warm before using them to wrap the fish. She said it will make the whole fish more tasty. To cook pepes ikan or spiced fish can be done in many ways; either you bake it in the oven, grill it, steam it in the pressure pan or cover it with burning ashes of charcoals in the ground. All will do! You decide!